African mediators trying to avert civil war in South Sudan say they have held "productive" talks with President Salva Kiir.

Ethiopian Foreign Minister Tedros Adhanom said consultations were continuing, but did not give details, according to BBC News.

Clashes began a week ago when President Kiir accused his former deputy, Riek Machar, of a failed coup.

U.S. Secretary of State John Kerry said he was sending a special envoy to help foster dialogue. He said his decision to send ambassador Donald Booth followed a phone conversation with President Kiir.

"Now is the time for South Sudan's leaders to rein in armed groups under their control, immediately cease attacks on civilians, and end the chain of retributive violence between different ethnic and political groups," Kerry said.

Hundreds of people have already died in fighting across the country.

Although Kiir has said he is ready for dialogue, Machar told French radio he was only ready to "negotiate his [Salva Kiir's] departure from power".

On Friday, Dec 20, President Kiir met foreign ministers from Ethiopia, Djibouti, Kenya, Sudan and Uganda who had travelled to the capital Juba to mediate in the crisis. He told them he agreed to "unconditional dialogue" to stop the violence.

"We had a very productive meeting with his Excellency President Salva Kiir and we will continue consultations," Adhanom, who led the delegation, told reporters before returning to the talks.

As the violence escalated, Ugandan troops flew to Juba on Friday to help evacuate their citizens. Military sources quoted by Reuters said they would also help secure the capital, which is about 75km (50 miles) from Uganda's border.

A number of other countries are also evacuating their nationals from South Sudan.

And with the fighting spreading to South Sudan's oilfields, China National Petroleum - one of the main operators - said it was evacuating workers back to Juba.

President Kiir, a member of the majority Dinka ethnic group, sacked Machar, who is from the Nuer community, in July.

He said that last Sunday night uniformed personnel opened fire at a meeting of the governing party, the Sudan People's Liberation Movement (SPLM).

Violence then broke out in Juba and has since spread across the country, pitting gangs of Nuer and Dinka against each other and sparking fears of a civil war.

The whereabouts of Machar, who has denied trying to stage a coup, remain unknown.